The present invention relates to a device for braking lines of tying twine, for agricultural machines of the type of balers, round balers and the like.
As is known, there is a widespread need to gather agricultural products of the type of grass, wheat, maize, hay, forage and the like, into bales of various shapes and sizes.
In fact, during the formation of the bales the agricultural products are compressed, thus reducing the overall space occupation: this evidently allows practical transport and easy storage, and more generally it makes them more easily available for subsequent processing, as a function of the specific purpose for which they are intended.
In order to obtain such result, agricultural machines are thus widely used which are known as “hay balers” or “forage balers”, within which a certainly major role is played by “round balers”, which produce cylindrical bales.
Round balers, like other similar agricultural machines, are capable of collecting the agricultural products from the ground and transferring them to a compression chamber, which is in turn provided with elements (rollers, belts or catenaries) arranged along the perimeter of the internal compartment of the chamber, in order to entrain and compress the products, in so doing resulting in the formation of the bale.
To ensure the holding of the configuration assumed by the agricultural products, and thus prevent the bale that has just been formed from breaking up, round balers are conveniently provided with contrivances that are capable of wrapping the bale with a polymeric film (or a net) or of tying it with a line of twine.
In more detail, in order to obtain the tying, round balers can be fitted with an apparatus that allows the controlled unreeling of a length of twine from a spool or from a skein (or the like), with which the bale is externally tied.
The apparatus is likewise capable of exerting a braking force on the line of twine, during its unreeling, so as to place the latter under tension, which is necessary in order to firmly hold the agricultural products in the desired format.
In conventional round balers, during each work cycle the tying apparatus is capable of exerting a braking force of variable intensity (as is often required by the applicative requirements), thanks to a plurality of elements that cooperate with each other in an exclusively mechanical manner.
Such implementation solution is not however devoid of drawbacks.
At the design stage, the mutual connection of the above mentioned mechanical elements is conveniently selected as a function of the law of variation of the braking force that it is desired to exert on the line of twine.
It thus appears evident that such law is determined uniquely by the design choices (and thus by the dimensioning and mutual placement of the elements involved). This does not allow any subsequent variation, if requirements dictate it, thus appreciably (and nowadays very unpopularly) reducing the versatility of the apparatus, which will be incapable of being adapted to a possible change of the working conditions of the baler.
Moreover, it must be noted that the same machine may be intended for different customers and different markets, and thus designed for the formation of bales of agricultural products of various different types, with weights, sizes and other chemical/physical properties which are often very different from each other (and their heterogeneity is further increased with the varying of the surrounding meteorological and climate conditions).
In such context, it seems clear that the impossibility of adapting the braking force to the various different types of agricultural product, as a function of the different resistance that each type offers, is a further serious limitation on the conventional solutions.
Lastly, it should be noted that, over time, the wear and natural deterioration of the mechanical elements can sometimes negatively influence correct operation, resulting in a progressive reduction of the braking effectiveness (and bale-tying effectiveness), with no possibility of remedying the situation except by way of complex, and costly, maintenance and repair activities.
The aim of the present invention is to solve the above mentioned problems, by providing a device that is capable of developing an adequate braking force during the tying of the bale.